Climate change: implications for Aussie cities

This Issue This is a part of the Urban design feature

By - , Build 99

Australia’s vulnerability to droughts, coastal erosion and temperature increases, along with its high greenhouse gas emissions, means it must take climate change seriously when looking at urban design for the future.

Aerial view of Melbourne’s urban sprawl. (Photo: Robert Kerton.)

Australia is one of the most urbanised countries in the world. Over 80% of the population live in cities (40% in Sydney and Melbourne, where the largest growth occurs). These cities are all contributing to climate change through large greenhouse gas emissions from energy consumption and car travel. There is increasing evidence indicating that these cities will suffer severe impacts from rising temperatures and a changing climate. This will affect building design and performance, including structural standards and cooling and heating demand.

Climatic confusion

A recent CSIRO report predicts Sydney’s future climate will be warmer and drier, with increased evaporation, heat waves, extreme winds, fire risk and extreme rainfall events. Higher temperatures will increase summer peak energy demand for air conditioning, increasing the risk of blackouts. Annual heat-related deaths in those aged over 65 in Sydney may increase from 176 at present to 1,312 by 2050.

Higher temperatures and lower average rainfall will severely affect water supply. Per capita water demand in Sydney would have to decline 54% by 2030 to meet reduced supply.

At the other end of the spectrum, increases in the intensity of heavy rainfall events and flash flooding will put strain on water infrastructure such as sewerage and drainage systems.

Aerial view of Melbourne’s urban sprawl. (Photo: Robert Kerton.)

It’s a gas, gas, gas

Australia has one of the highest greenhouse gas emissions rates (per capita) in the world (28 tonnes/year). The 2006 report ‘Australia: State of the Environment’ reveals that urban energy use is projected to grow significantly. After the United States, Australia has the lowest urban density in the world. Urban travel per capita is expected to increase 12% by 2020 with total vehicle kilometres travelled going up by 33%.

Australian cities have been built around the car, creating a culture heavily reliant on private car access. To reduce greenhouse gas emissions from travel, the focus is to minimise the sprawl of outer suburbia and to encourage higher density residential development served with public transport. This is already a common theme in most metropolitan plans.

The Victorian Government strategy ‘Melbourne 2030’ seeks to concentrate almost 70 percent of planned new dwellings within existing urban boundaries, and raise the proportion of public transport trips.

The NSW Government ‘Metropolitan Strategy’ plans for 60–70% of housing development to take place in established areas over the next 25 to 30 years.

The Queensland Government ‘South East Queensland Regional Plan’ seeks to accommodate 40–50% of the planned 575,000 new dwellings by 2026 through infill or in activity centres, and to limit outer urban development.

Integrating land use and transport planning is essential for a successful compact city, yet relatively little has been spent on improving public transport infrastructure, particularly to connect new outer suburbs.

Urban heat islands

Asphalt and concrete store the sun’s energy and remain hot long after sunset. With the combined effect of cars and air conditioners generating heat, air temperatures stay several degrees higher over large cities than over adjacent rural areas, leading to an ‘urban heat island’ effect. In a vicious circle, energy demand from air conditioning increases to cope with the increased urban temperatures, further adding to the heating effect.

Many cities around the world are tackling this effect by ‘greening’ their cities. Trees are planted in strategic locations and green roofs are added to keep buildings cool. There is the extra benefit of providing storm water buffers to reduce flood risk.

Climate-friendly design

We know that the impact of our present fossil fuel-based, centralised energy supply system is unsustainable and adds to global warming. Since most of our energy use is either in or for cities, new ways are being developed to supply and use energy.

Good building design and appropriate insulation can significantly reduce energy consumption and greenhouse gas emissions. Well-designed residential developments with solar photovoltaic, solar hot water and passive solar design, would have a very low energy bill and lower greenhouse gas contributions.

The Australian Government’s Sustainable Cities vision recognises solar power as an energy system that can result in significant savings: ‘… if each of the 1.8 to 2 million homes in Sydney installed a 1-kilowatt solar power system on its roof, we would defer the need to build a new power station for 50 to 80 years.’

Some mandated codes targeting the energy efficiency of new housing are the NSW BASIX code and Victorian 5 Star housing requirement. There are also a number of voluntary residential energy performance assessment guides available.

Urban trends

The implications of climate change for urban design in Australia can be summarised in five main characteristics. Australian cities will have to become: denser; greener; more energy efficient; better serviced by public transport; and better adapted to deal with more frequent extreme weather events.

Government regulation is facilitating these changes, and the building industry is also changing to contribute to fabricating a ‘climate change appropriate’ built environment.

For more

On the implications of climate change for urban design in Australia can be found on the following websites: www.aph.gov.au, www.greenhouse.gov.au/yourhome, www.greensmart.com.au, www.environment.gov.au/soe/2006 and www.greenhouseinfo.nsw.gov.au.

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Articles are correct at the time of publication but may have since become outdated.

Aerial view of Melbourne’s urban sprawl. (Photo: Robert Kerton.)

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